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Current File : //usr/share/emscripten/tests/poppler/poppler/CairoRescaleBox.cc /* -*- Mode: c; c-basic-offset: 4; tab-width: 8; indent-tabs-mode: t; -*- */
/*
* Copyright © 2009 Mozilla Corporation
*
* Permission to use, copy, modify, distribute, and sell this software and its
* documentation for any purpose is hereby granted without fee, provided that
* the above copyright notice appear in all copies and that both that
* copyright notice and this permission notice appear in supporting
* documentation, and that the name of Mozilla Corporation not be used in
* advertising or publicity pertaining to distribution of the software without
* specific, written prior permission. Mozilla Corporation makes no
* representations about the suitability of this software for any purpose. It
* is provided "as is" without express or implied warranty.
*
* MOZILLA CORPORATION DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
* INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT
* SHALL MOZILLA CORPORATION BE LIABLE FOR ANY SPECIAL, INDIRECT OR
* CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
* DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
* TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
* OF THIS SOFTWARE.
*
* Author: Jeff Muizelaar, Mozilla Corp.
*/
/* This implements a box filter that supports non-integer box sizes */
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <stdint.h>
#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
#include <math.h>
#include "goo/gmem.h"
#include "CairoRescaleBox.h"
typedef unsigned short int uint16_t;
typedef unsigned int uint32_t;
/* we work in fixed point where 1. == 1 << 24 */
#define FIXED_SHIFT 24
static void downsample_row_box_filter (
int start, int width,
uint32_t *src, uint32_t *dest,
int coverage[], int pixel_coverage)
{
/* we need an array of the pixel contribution of each destination pixel on the boundaries.
* we invert the value to get the value on the other size of the box */
/*
value = a * contribution * 1/box_size
value += a * 1/box_size
value += a * 1/box_size
value += a * 1/box_size
value += a * (1 - contribution) * 1/box_size
a * (1/box_size - contribution * 1/box_size)
box size is constant
value = a * contribtion_a * 1/box_size + b * contribution_b * 1/box_size
contribution_b = (1 - contribution_a)
= (1 - contribution_a_next)
*/
/* box size = ceil(src_width/dest_width) */
int x = 0;
/* skip to start */
/* XXX: it might be possible to do this directly instead of iteratively, however
* the iterative solution is simple */
while (x < start)
{
int box = 1 << FIXED_SHIFT;
int start_coverage = coverage[x];
box -= start_coverage;
src++;
while (box >= pixel_coverage)
{
src++;
box -= pixel_coverage;
}
x++;
}
while (x < start + width)
{
uint32_t a = 0;
uint32_t r = 0;
uint32_t g = 0;
uint32_t b = 0;
int box = 1 << FIXED_SHIFT;
int start_coverage = coverage[x];
a = ((*src >> 24) & 0xff) * start_coverage;
r = ((*src >> 16) & 0xff) * start_coverage;
g = ((*src >> 8) & 0xff) * start_coverage;
b = ((*src >> 0) & 0xff) * start_coverage;
src++;
x++;
box -= start_coverage;
while (box >= pixel_coverage)
{
a += ((*src >> 24) & 0xff) * pixel_coverage;
r += ((*src >> 16) & 0xff) * pixel_coverage;
g += ((*src >> 8) & 0xff) * pixel_coverage;
b += ((*src >> 0) & 0xff) * pixel_coverage;
src++;
box -= pixel_coverage;
}
/* multiply by whatever is leftover
* this ensures that we don't bias down.
* i.e. start_coverage + n*pixel_coverage + box == 1 << 24 */
if (box > 0)
{
a += ((*src >> 24) & 0xff) * box;
r += ((*src >> 16) & 0xff) * box;
g += ((*src >> 8) & 0xff) * box;
b += ((*src >> 0) & 0xff) * box;
}
a >>= FIXED_SHIFT;
r >>= FIXED_SHIFT;
g >>= FIXED_SHIFT;
b >>= FIXED_SHIFT;
*dest = (a << 24) | (r << 16) | (g << 8) | b;
dest++;
}
}
static void downsample_columns_box_filter (
int n,
int start_coverage,
int pixel_coverage,
uint32_t *src, uint32_t *dest)
{
int stride = n;
while (n--) {
uint32_t a = 0;
uint32_t r = 0;
uint32_t g = 0;
uint32_t b = 0;
uint32_t *column_src = src;
int box = 1 << FIXED_SHIFT;
a = ((*column_src >> 24) & 0xff) * start_coverage;
r = ((*column_src >> 16) & 0xff) * start_coverage;
g = ((*column_src >> 8) & 0xff) * start_coverage;
b = ((*column_src >> 0) & 0xff) * start_coverage;
column_src += stride;
box -= start_coverage;
while (box >= pixel_coverage)
{
a += ((*column_src >> 24) & 0xff) * pixel_coverage;
r += ((*column_src >> 16) & 0xff) * pixel_coverage;
g += ((*column_src >> 8) & 0xff) * pixel_coverage;
b += ((*column_src >> 0) & 0xff) * pixel_coverage;
column_src += stride;
box -= pixel_coverage;
}
if (box > 0) {
a += ((*column_src >> 24) & 0xff) * box;
r += ((*column_src >> 16) & 0xff) * box;
g += ((*column_src >> 8) & 0xff) * box;
b += ((*column_src >> 0) & 0xff) * box;
}
a >>= FIXED_SHIFT;
r >>= FIXED_SHIFT;
g >>= FIXED_SHIFT;
b >>= FIXED_SHIFT;
*dest = (a << 24) | (r << 16) | (g << 8) | b;
dest++;
src++;
}
}
static int compute_coverage (int coverage[], int src_length, int dest_length)
{
int i;
/* num = src_length/dest_length
total = sum(pixel) / num
pixel * 1/num == pixel * dest_length / src_length
*/
/* the average contribution of each source pixel */
int ratio = ((1 << 24)*(long long int)dest_length)/src_length;
/* because ((1 << 24)*(long long int)dest_length) won't always be divisible by src_length
* we'll need someplace to put the other bits.
*
* We want to ensure a + n*ratio < 1<<24
*
* 1<<24
* */
double scale = (double)src_length/dest_length;
/* for each destination pixel compute the coverage of the left most pixel included in the box */
/* I have a proof of this, which this margin is too narrow to contain */
for (i=0; i<dest_length; i++)
{
float left_side = i*scale;
float right_side = (i+1)*scale;
float right_fract = right_side - floor (right_side);
float left_fract = ceil (left_side) - left_side;
int overage;
/* find out how many source pixels will be used to fill the box */
int count = floor (right_side) - ceil (left_side);
/* what's the maximum value this expression can become?
floor((i+1)*scale) - ceil(i*scale)
(i+1)*scale - i*scale == scale
since floor((i+1)*scale) <= (i+1)*scale
and ceil(i*scale) >= i*scale
floor((i+1)*scale) - ceil(i*scale) <= scale
further since: floor((i+1)*scale) - ceil(i*scale) is an integer
therefore:
floor((i+1)*scale) - ceil(i*scale) <= floor(scale)
*/
if (left_fract == 0.)
count--;
/* compute how much the right-most pixel contributes */
overage = ratio*(right_fract);
/* the remainder is the the amount that the left-most pixel
* contributes */
coverage[i] = (1<<24) - (count * ratio + overage);
}
return ratio;
}
GBool downscale_box_filter(uint32_t *orig, int orig_stride, unsigned orig_width, unsigned orig_height,
signed scaled_width, signed scaled_height,
uint16_t start_column, uint16_t start_row,
uint16_t width, uint16_t height,
uint32_t *dest, int dst_stride)
{
int pixel_coverage_x, pixel_coverage_y;
int dest_y;
int src_y = 0;
uint32_t *scanline = orig;
int *x_coverage = NULL;
int *y_coverage = NULL;
uint32_t *temp_buf = NULL;
GBool retval = gFalse;
x_coverage = (int *)gmallocn3 (orig_width, 1, sizeof(int));
y_coverage = (int *)gmallocn3 (orig_height, 1, sizeof(int));
/* we need to allocate enough room for ceil(src_height/dest_height)+1
Example:
src_height = 140
dest_height = 50
src_height/dest_height = 2.8
|-------------| 2.8 pixels
|----|----|----|----| 4 pixels
need to sample 3 pixels
|-------------| 2.8 pixels
|----|----|----|----| 4 pixels
need to sample 4 pixels
*/
temp_buf = (uint32_t *)gmallocn3 ((orig_height + scaled_height-1)/scaled_height+1, scaled_width, sizeof(uint32_t));
if (!x_coverage || !y_coverage || !scanline || !temp_buf)
goto cleanup;
pixel_coverage_x = compute_coverage (x_coverage, orig_width, scaled_width);
pixel_coverage_y = compute_coverage (y_coverage, orig_height, scaled_height);
assert (width + start_column <= scaled_width);
/* skip the rows at the beginning */
for (dest_y = 0; dest_y < start_row; dest_y++)
{
int box = 1 << FIXED_SHIFT;
int start_coverage_y = y_coverage[dest_y];
box -= start_coverage_y;
src_y++;
while (box >= pixel_coverage_y)
{
box -= pixel_coverage_y;
src_y++;
}
}
for (; dest_y < start_row + height; dest_y++)
{
int columns = 0;
int box = 1 << FIXED_SHIFT;
int start_coverage_y = y_coverage[dest_y];
scanline = orig + src_y * orig_stride / 4;
downsample_row_box_filter (start_column, width, scanline, temp_buf + width * columns, x_coverage, pixel_coverage_x);
columns++;
src_y++;
box -= start_coverage_y;
while (box >= pixel_coverage_y)
{
scanline = orig + src_y * orig_stride / 4;
downsample_row_box_filter (start_column, width, scanline, temp_buf + width * columns, x_coverage, pixel_coverage_x);
columns++;
src_y++;
box -= pixel_coverage_y;
}
/* downsample any leftovers */
if (box > 0)
{
scanline = orig + src_y * orig_stride / 4;
downsample_row_box_filter (start_column, width, scanline, temp_buf + width * columns, x_coverage, pixel_coverage_x);
columns++;
}
/* now scale the rows we just downsampled in the y direction */
downsample_columns_box_filter (width, start_coverage_y, pixel_coverage_y, temp_buf, dest);
dest += dst_stride / 4;
// assert(width*columns <= ((orig_height + scaled_height-1)/scaled_height+1) * width);
}
// assert (src_y<=orig_height);
retval = gTrue;
cleanup:
free (x_coverage);
free (y_coverage);
free (temp_buf);
return gTrue;
}
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